1. Field of the Invention
The present invention relates to the field of oilfield drilling equipment, and in particular to rotating control devices.
2. Description of the Related Art
Conventional offshore drilling techniques involve using hydraulic pressure generated by a preselected fluid inside the wellbore to control pressures in the formation being drilled. However, a majority of known resources, gas hydrates excluded, are considered economically undrillable with conventional techniques. Pore pressure depletion, the need to drill in deeper water, and increasing drilling costs indicate that the amount of known resources considered economically undrillable will continue to increase. Newer techniques, such as underbalanced drilling and managed pressure drilling, have been used to control pressure in the wellbore. These techniques present a need for pressure management devices, such as rotating control devices (RCDs) and diverters.
RCDs have been used in conventional offshore drilling. An RCD is a drill-through device with a rotating seal that contacts and seals against the drill string (drill pipe, casing, drill collars, kelly, etc.) for the purposes of controlling the pressure or fluid flow to the surface. Rig operators typically bolt a conventional RCD to a riser below the rotary table of a drilling rig. However, such a fixed connection has presented health, safety, and environmental (HSE) problems because retrieving the RCD has required unbolting the RCD from the riser, requiring personnel to go below the rotary table of the rig in the moon pool to disconnect the RCD. In addition to the HSE concerns, the retrieval procedure is complex and time consuming, decreasing the operational efficiency of the rig. Furthermore, space in the area above the riser typically limits the drilling rig operator's ability to install equipment on top of the riser.
U.S. Pat. No. 6,129,152 proposes a flexible rotating bladder and seal assembly that is hydraulically latchable with its rotating blow-out preventer housing. U.S. Pat. No. 6,457,529 proposes a circumferential ring that forces dogs outward to releasably attach an RCD with a manifold. U.S. Pat. No. 7,040,394 proposes inflatable bladders/seals. U.S. Pat. No. 7,080,685 proposes a rotatable packer that may be latchingly removed independently of the bearings and other non-rotating portions of the RCD. The '685 patent also proposes the use of an indicator pin urged by a piston to indicate the position of the piston. It is also known in the prior art to manually check the position of a piston in an RCD with a flashlight after removal of certain components of the RCD. However, this presents HSE problems as it requires personnel to go below the rotary table of the rig to examine the RCD, and it is time consuming.
Pub. No. US 2004/0017190 proposes a linear position sensor and a degrading surface to derive an absolute angular position of a rotating component. U.S. Pat. No. 5,243,187 proposes a body having a plurality of saw tooth-shaped regions which lie one behind the other, and two distance sensors for determining a rotational angle or displacement of the body.
The above discussed U.S. Pat. Nos. 5,243,187; 6,129,152; 6,457,529; 7,040,394; and 7,080,685; and Pub. No. US 2004/0017190 are hereby incorporated by reference for all purposes in their entirety. U.S. Pat. Nos. 6,129,152; 7,040,394 and 7,080,685 are assigned to the assignee of the present invention.
It would be desirable to retrieve an RCD or other oilfield device positioned below the rotary table of the rig without personnel having to go below the rotary table. It would also be desirable to remotely determine with confidence the position of the latch(s) relative to an RCD.